Fluidic pumping systems such as those presently widely utilized in domestic water supply applications often employ a pressure switch which turns an electrically driven pump on when the system pressure falls below a predetermined cut-in pressure and turns the pump off when the system pressure rises above a predetermined cut-out pressure. Such systems often incorporate a conventional diaphragm tank which includes both pressurized air and system fluid separated by a flexible bladder or other element. Diaphragm tanks are desirable from an operational standpoint as they may reduce cycling of the pump by providing a limited amount of fluidic capacitance in the supply system. Systems of this type, however, may be characterized by supply pressure which varies, depending both on the amount of fluid in the tank as well as the operational state of the pump. Supply pressure variability is generally undesirable from the standpoint of a user. Such systems are also relatively expensive to procure initially as well as maintain due to the initial cost and limited life of both the diaphragm tank and pump motor. Additionally, the tank displaces a relatively large volume thereby requiring accommodation of the apparatus in a zone of sufficient size which might otherwise be utilized for more advantageous purposes.
A recent substantial improvement in fluidic pumping systems useful in applications of the aforementioned type is disclosed in U.S. Pat. No. 5,190,443 entitled Hydropneumatic Constant Pressure Device, granted to Valdes on Mar. 2, 1993, the disclosure of which is herein incorporated by reference. Briefly, the improved system disclosed therein includes a motor driven pump controlled by a pressure switch mounted to an hydraulic actuator port which is selectively isolated from internal system pressure during periods of consumption demand above a predetermined flow rate. Firstly, by operating the pump continuously during periods of demand, the system advantageously supplies a substantially constant pressure output. Further, depending on the particular application, pump motor cycling may be reduced significantly and the concomitant reduction in motor life associated therewith avoided. Additionally, the system obviates the cost and space claim associated with large, short-lived diaphragm tanks, system capacitance being provided by a small hydropneumatic arrangement as disclosed therein.